This invention relates to a process for producing in high yields substantially pure phosphorochloridothionate (hereinafter "thionate").
The thionates produced by the process of this invention have the general formula: ##STR1## wherein R.sub.1 and R.sub.2 are each alkyl substituents of 1 to 12 carbon atoms. The thionates are valuable intermediates in the manufacture of pesticidal agents, flotation agents, plasticizers, lubricating oil additives, rubber curing compounds, flame retardants and many other useful chemicals.
Various processes have been utilized for the production and purification of the aforementioned thionates for example:
(1) U.S. Pat. No. 3,897,523 to Sorstokke; PA1 (2) U.S. Pat. No. 3,794,703 to Beck et al; PA1 (3) U.S. Pat. No. 3,502,750 to Anglaret; PA1 (4) U.S. Pat. No. 3,356,774 to Niermann et al; PA1 (5) U.S. Pat. No. 3,098,866 to Divine; PA1 (6) U.S. Pat. No. 3,089,800 to Chupp et al; PA1 (7) U.S. Pat. No. 2,900,406 to Vogel et al; PA1 (8) U.S. Pat. No. 2,715,136 to Toy et al; PA1 (9) U.S. Pat. No. 2,692,893 to Hechenbleikner; PA1 (10) U.S. Pat. No. 2,482,063 to Hechenbleikner; PA1 (11) British Pat. No. 646,188 to Hechenbleikner; PA1 (12) British Pat. No. 1,289,396 to Hercules, Inc.; and PA1 (13) German Pat. No. 1,801,432 to Knapsack, AG.
The entire disclosures of all of the aforementioned references are incorporated herein by reference.
Generally, commercial quantities of thionates are obtained by chlorinating an initial reactant composition with a chlorinating agent, the reactant composition containing at least one compound which is either:
(1) A bis(phosphorothioic) sulfide of the general formula: ##STR2## wherein m is a whole number, preferably 2; or
(2) a thioic acid or salt thereof having the general formula: ##STR3## wherein M is hydrogen, ammonium, an alkaline earth metal or an alkali metal. The chlorinating step produces a crude thionate reaction mixture which contains the thionate and impurities. The crude reaction mixture is usually purified.
The chlorinating agents which can be employed include chlorine, sulfur dichloride, sulfur monochloride, sulfuryl chloride and phosphorus pentachloride.
A process for producing a thionate by chlorinating a bis(phosphorothioic) sulfide is more fully described in, for example, the aforementioned U.S. Pat. No. 2,482,063 to Hechenbleikner.
A process for producing a thionate by chlorinating a thioic acid or salt thereof is more fully described in, for example, the aforementioned U.S. Pat. No. 2,692,893 and British Pat. No. 646,188 to Hechenbleikner.
As indicated the aforementioned processes produce by-product impurities. Illustrative of some of the processes employed to produce thionates and the by-product impurities produced therefrom are the following, wherein M is as previously defined and wherein X is the grouping ##STR4##
__________________________________________________________________________ Chlorinating By-Product Reactant Agent Thionate Impurities __________________________________________________________________________ (a) 2 XSM + 3 Cl.sub.2 .fwdarw. 2 XCl + 2 MCl + S.sub.2 Cl.sub.2 (b) 2 XSM + 2 Cl.sub.2 .fwdarw. 2 XCl + 2 MCl + 2 S (c) 2 XSM + 2 S.sub.2 Cl.sub.2 .fwdarw. 2 XCl + 2 MCl + 6 S (d) 2 XSM + 2 SCl.sub.2 .fwdarw. 2 XCl + 2 MCl + 2 S (e) 2 XSM + 6 SCl.sub.2 .fwdarw. 2 XCl + 2 MCl + 4 S.sub.2 Cl.sub.2 (f) 2 XSM + 2 SO.sub.2 Cl.sub.2 .fwdarw. 2 XCl + 2 MCl+2S+2 SO.sub.2 (g) 2 XSM + Cl.sub.2 .fwdarw. (X).sub.2 S.sub.2 + 2 MCl (h) 2 XSM + S.sub.2 Cl.sub.2 .fwdarw. (X).sub.2 S.sub.4 + 2 MCl (i) 2 XSM + 2 Cl.sub.2 .fwdarw. (X).sub.2 S.sub.2 + 2 MCl+S.sub.2 Cl.sub.2 (j) 2 XSM + SO.sub.2 Cl.sub.2 .fwdarw. (X).sub.2 S.sub.2 + 2 MCl + SO.sub.2 (k) (X).sub.2 S.sub.2 + 2 Cl.sub.2 .fwdarw. 2 XCl + S.sub.2 Cl.sub.2 (l) (X).sub.2 S.sub.2 + Cl.sub.2 .fwdarw. 2 XCl + 2S (m) (X).sub.2 S.sub.2 + S.sub.2 Cl.sub.2 .fwdarw. 2 XCl + 4S (n) (X).sub.2 S.sub.2 + 4SCl.sub. 2 .fwdarw. 2 XCl + 3 S.sub.2 Cl.sub.2 (o) (X).sub.2 S.sub.2 + SO.sub.2 Cl.sub.2 .fwdarw. 2 XCl + 2S (p) (X).sub.2 S.sub.2 + 2SO.sub. 2 Cl.sub.2 .fwdarw. 2 XCl + S.sub.2 Cl.sub.2 + 2 SO.sub.2 (q) (X).sub.2 S.sub.3 + S.sub.2 Cl.sub.2 .fwdarw. 2 XCl + 5S (r) (X).sub.2 S.sub.4 + S.sub.2 Cl.sub.2 .fwdarw. 2 XCl + 6S __________________________________________________________________________
For example, in a typical type (k) reaction bis(O,O-diethyl phosphorothioic) disulfide is reacted with chlorine to produce O,O-diethyl chlorothiophosphate as follows: ##STR5##
This reaction produces sulfur monochloride as a by-product impurity.
In a typical type (a) reaction O,O-diethyl dithiophosphoric acid is reacted with chlorine to produce O,O-diethyl chlorothiophosphate as follows: ##STR6##
This reaction produces sulfur monochloride and hydrogen chloride as by-product impurities.
Additional impurities may, for example be introduced if the thionate is produced in a two step process. A typical two step process involves treating alcohol with a phosphorus sulfur compound to produce a crude thioic acid composition: ##STR7## wherein, for example, R is an alkyl substituent having from 1 to 12 carbon atoms. The crude thioic acid reaction mixture is difficult to purify. It is generally used as the initial reactant composition which is directly chlorinated to produce a crude thionate reaction mixture. The crude thionate reaction mixture produced from this two step process, not only has the by-product impurities produced from the chlorination step, but additionally may have contained therein hydrogen sulfide, unreacted alcohol, or the chlorinated products thereof.
Thus, as can be seen from the foregoing, the crude thionate reaction mixture may have contained therein various quantities of by-product impurities such as MCl, S.sub.2 Cl.sub.2, S, SO.sub.2,(X).sub.2 S.sub.2,H.sub.2 S unreacted alcohol, the chlorinated products of H.sub.2 S and unreacted alcohol, unreacted XSM and unreacted chlorinating agent from which the thionate must be separated. A substantial portion of the impurities in the crude thionate reaction mixture is usually sulfur monochloride.
In addition, there are a variety of side reaction impurities which are formed to varying extents depending upon the reaction conditions and the reactants, i.e. the type and amount of chlorinating agent as well as the purity of the bis(phosphorothioic) sulfide or thioic acid or salt thereof subjected to chlorination, which further contaminate the crude thionate reaction mixture.
For example, the crude thionate reaction mixture may be additionally contaminated with side reaction impurities some of which satisfy the structure ##STR8## wherein n is 0 or 1, and R is R.sub.1 or R.sub.2. For example, these side reaction impurities may include one or more compounds having the groups ##STR9## wherein the unsatisfied valences are satisfied by R.sub.1 and/or R.sub.2.
The need for improving the quality of the crude thionate reaction mixture is readily apparent in subsequent processes employing the same and in the products derived therefrom. Unless a substantially pure thionate is employed, the efficiency of processes employed in preparing derivatives is substantially lowered. For example, the impurity ##STR10## (wherein the unsatisfied valence is satisfied by R.sub.1 or R.sub.2), which may be obtained in substantial amounts from the chlorination process, contains twice as many reactive groups (i.e. chlorine substituents) as the desired thionate. Additionally, this impurity contains the ##STR11## which reacts to products which do not have the desirable properties of the corresponding thionate derivatives.
Many attempts have been made to remove the impurities from crude thionate reaction mixture in order to produce a purer thionate product, for example: